Pastor Youcef Nadarkhani, the head of a network of Christian house churches in Iran, could be executed as soon as midnight Wednesday in Tehran for refusing to recant his religious beliefs and convert to Islam, said the chair of a commission that monitors religious freedom around the world.

A statement by the United States Commission on International Religious Freedom, an independent advisory group appointed by the president and Congress, "expressed deep concern" for the man's fate.

After four days of an appeals trial for apostasy, Nadarkhani refused to recant his beliefs.

Leonard Leo, chair of the commission, said the pastor "is being asked to recant a faith he has always had. Once again, the Iranian regime has demonstrated that it practices hypocritical barbarian practices."

Leo said that while the trial is closed to the press, the commission collects information from sources in Iran and around the world. A release by the group says their responsibility is to "review the facts and circumstances of violations of religious freedom internationally."

"I would be disappointed if at the end of this whole maelstrom, there was no statement by our government on this situation," Leo said. "At some point the United States has to stand up for the right of this pastor and for human rights more broadly and call countries to account for what they are doing."

The commission's statement also called the trial a sham and said Iran is violating the International Covenant on Civil and Political Rights, to which Iran is a party.

Nadarkhani was first sentenced to execution in November 2010, the commission said, and in order to avoid the death penalty, he is being asked to recant his beliefs and convert to Islam. Leo said an apostasy trial is rare in Iran; the last occurred in 1990.

Iran's claim stems from the pastor's Muslim parents. According to Leo, the court needed to verify if Nadarkhani had ever been a Muslim. In order to be given what Iran looks at as the opportunity to recant his beliefs, Nadarkhani must have never been a Muslim before the age of 15, Leo said.

Because for the last four days in court he was given the opportunity, it is apparent that the Iranian court found he was never a Muslim and therefore Nadarkhani could have converted.

According to a source close to the situation within the Commission on International Religious Freedom, Ayatollah Ali Khamenei, the Supreme Leader of Iran, would have to sign off on the execution. Speaking on the condition of anonymity because of the subject's sensitivity, the source said these types of issues are always difficult with Iran because of the lack of transparency in how they make decisions on when and how to act.

The source also said that in the past, political prisoners have had their prison time and punishment reduced by the Iranian government. Though they did not say that was guaranteed in this situation, the source indicated it was a possibility.

The American Center for Law and Justice, a right-leaning organization founded by television evangelist Pat Robertson, reported Wednesday night that Nadarkhani's death sentence punishment had been overturned, meaning that the pastor would be receiving a lower punishment than death. They sourced the claim to someone in Iran.

Those reports could not be verified by CNN. The Permanent Mission of the Islamic Republic of Iran in the United Nations failed to comment on the ruling.

Jordan Sekulow, executive director of the ACLJ, said the outcry from Christians in America has been loud and sustained.

"American Christian, like never before, are engaged in this," Sekulow said. "This is evidence that Christians in America over the past decade have done a better job engaging in the persecution issue."

Sekulow also said he hopes the White House or State Department will issue a statement on the issue.